Catalytic Conjugate Addition of Acyl Anion Equivalents Promoted by Fluorodesilylation

Abstract

The conjugate addition of acyl anion equivalents derived from 2-silyl-1,3-dithianes to α,β-unsaturated ketones and esters has been achieved using a substoichiometric amount of TBAF. High yields and short reaction times are observed for the addition of aryl-1,3-dithianes to a variety of cyclic and acyclic α,β-unsaturated carbonyl acceptors. Observation of the reactive anion by (13)C NMR spectroscopy and extension to an asymmetric variant is also presented.

Boron-promoted Deprotonative Conjugate Addition: Development of Geminal diborons as Versatile Soft Pronucleophiles and Acyl An-ion Equivalents

“…There has been considerable interest in development of new types of umpolung reagents due to their utility in accessing carbonyl compounds having 1,4 functional group relationships. 21,22 Given the facile reactivity of 1 as soft nucleophiles (Scheme 1-2) and the mild conditions required for oxidation of boronate group, 12,15 we hypothesized that a one-pot conjugate addition-diboron oxidation sequence could be feasible. The resulting 1,4-dicarbonyl products are privileged intermediates for synthesis of bioactive compounds.…”

A Highly EfficientN‐Mesityl Thiazolylidene for the Aliphatic Stetter Reaction: Stereoelectronic Quantification for Comparison of N‐Heterocyclic Carbene Organocatalysts

“…In contrast to 1,4‐dicarbonyls in general, the synthesis of 1,4‐diketones poses a greater challenge, often requiring use of an excess of one coupling partner and/or significant pre‐functionalisation of substrates to achieve the desired heterocoupling. Reported methods include oxidative homocoupling [23–27] or heterocoupling of ketone enolates, [7,24,28–34,35,36] alkylation of enolates, [9,14,37–42] alkylation of acyl anion equivalents [43–47] or acyl radicals, [11,48] acylation of homoenolate equivalents, [12,13,49–52] or multicomponent strategies [53,54] . Only a subset of methods have been reported that tolerate aliphatic substrates for both reaction partners: addition of silyl enolates to oxyallyl zwitterions [10] and the aldehyde umpolung‐based Stetter reaction [4,5,45,55] …”

“…[8,[15][16][17][18][19][20][21][22] In contrast to 1,4-dicarbonyls in general, the synthesis of 1,4-diketones poses a greater challenge, often requiring use of an excess of one coupling partner and/or significant pre-functionalisation of substrates to achieve the desired heterocoupling. Reported methods include oxidative homocoupling [23][24][25][26][27] or heterocoupling of ketone enolates, [7,24,[28][29][30][31][32][33][34]35,36] alkylation of enolates, [9,14,[37][38][39][40][41][42] alkylation of acyl anion equivalents [43][44][45][46][47] or acyl radicals, [11,48] acylation of homoenolate equivalents, [12,13,[49][50][51][52] or multicomponent strategies. [53,…”

Direct Regioselective [3 + 2]-Cyclization Reactions of Ambivalent Electrophilic/Nucleophilic β-Chlorovinyl Dithianes: Access to Cyclopentene Derivatives

“…In general, α,β-unsaturated carbonyl compounds constitute one of the most frequently used electrophiles that readily accommodate an appropriate nucleophile . Nevertheless, alternative synthetic methods have been developed for the successful formation of allenol/allenolates or vinyl carbanions from α,β-unsaturated compounds .…”